You are answering a USMLE-style medical question. Question: A 54-year-old man comes to the emergency department because of a 2-day history of increasingly severe abdominal pain, nausea, and bilious vomiting. His last bowel movement was yesterday and he has not passed flatus since then. He underwent appendectomy at the age of 39. He has psoriasis, hypertension, type 2 diabetes mellitus, and chronic back pain. He drinks two beers daily. He takes a topical corticosteroid, ramipril, metformin, and ibuprofen daily. He is 176 cm (5 ft 9 in) tall and weighs 108 kg (240 lb); BMI is 35.4 kg/m2. His temperature is 36.8°C (98.4°F), respirations are 15/min, pulse is 90/min, and blood pressure is 112/67 mm Hg. Examination shows thick, scaly, plaques over both elbows and knees. Abdominal examination shows three well-healed laparoscopic scars. The abdomen is distended and there are frequent, high-pitched bowel sounds on auscultation. Digital rectal examination shows an empty rectum. Laboratory studies show: Hematocrit 44% Leukocyte count 9,000/mm3 Platelet count 225,000/mm3 Serum Na+ 139 mEq/L K+ 4.1 mEq/L Cl− 101 mEq/L HCO3− 26 mEq/L Glucose 95 mg/dL Creatinine 1.1 mg/dL Alkaline phosphatase 78 U/L Aspartate aminotransferase (AST, GOT) 19 U/L Alanine aminotransferase (ALT, GPT) 14 U/L γ-Glutamyltransferase (GGT) 52 U/L (N=5–50 U/L) Hemoglobin A1C 6.4% Abdominal ultrasound shows nonpropulsive peristalsis of the small bowel. Which of the following is the most likely cause of this patient's condition?" Options: A) Chronic inflammatory bowel disease B) Ibuprofen C) History of abdominal surgery D) Alcohol Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.